Nonetheless, Friday's telephone call -- Obama at his desk in the Oval Office, Rouhani in a limousine on the way to the airport after diplomatic meetings at the United Nations -- marked one of the most hopeful steps toward reconciliation in decades.
"This is part of a pattern that has led to a real breakthrough," said Iran scholar Gary Sick at Columbia University. "And basically what's happening is that the ice that has covered the U.S.-Iran relationship for over the last 30 years is starting to break. And when ice starts to break up, it goes faster than you think. This is breathtaking."
Obama came out to the White House briefing room to announce the conversation about an hour after the call ended.
"I do believe that there is a basis for resolution," Obama said. He said an agreement could usher in a new era of mutual interest and respect between the United States and Iran, but he also said it would require Iran to take "meaningful, transparent and verifiable actions" concerning its nuclear program.
"A path to a meaningful agreement will be difficult and, at this point, both sides have significant concerns that will have to be overcome," Obama said, "but I believe we've got a responsibility to pursue diplomacy and that we have a unique opportunity to make progress with the new leadership in Tehran."
Iran's official news agency said the two leaders "underlined the need for a political will for expediting resolution of West's standoff with Iran over the latter's nuclear program." The White House said the United States wants to move "expeditiously" on Iranian negotiations but isn't setting a hard deadline.
Mahmoud Ahmadinejad, Rouhani's predecessor, had trouble with the supreme leader when Ahmadinejad attempted to challenge his power. The backlash weakened Ahmadinejad's government and left him with less political power.
Rouhani was elected in June and took office Aug. 4 after campaigning on a promise to seek relief from U.S. and Western sanctions that have slashed Iran's oil exports by more than half in the past two years, caused inflation to spike and undercut the value of the nation's currency.
At issue most directly right now are suspicions outlined in reports from the U.N.'s International Atomic Energy Agency that Iran has worked secretly on trying to develop nuclear weapons. Tehran says it isn't interested in atomic arms and only wants to develop nuclear technology for peaceful use.